BOB MOON: Agriculture ministers from across Europe are holding an urgent meeting today. And the European Union's health chief is warning Germany against making premature conclusions about the source of contaminated food that's already killed 22 people, and cost farmers billions in exports. It's reminiscent of the big E. coli scare here in the U.S. a couple of years ago when federal regulators struggled for month to pinpoint the source.

Our thanks to the BBC's Tristana Moore for joining us now from Berlin.

TRISTANA MOORE: Hello.

MOON: First they thought it was Spanish cucumbers, then German spouts -- both of which have turned out to be wrong. Where are they looking next?

MOORE: Well, I think they're still looking at spouts really. Because over the weekend, the German authorities pointed the finger of blame at bean spouts. Initial tests suggest that these locally grown bean spouts were the likely source of the bacterial outbreak, which has killed so far 22 people in Germany and infect hundreds more. And the spouts haven't been given the all-clear yet.

MOON: Now I saw a report that Spanish produce growers lost an estimated $600 million in exports last week after they got the initial erroneous blame for this. Why does it seem to be so hard to figure out where this food contamination is coming from?

MOORE: Dr. John Cowden of the Consultant for Health Protection in Scotland -- where they also had an E. coli outbreak a couple of years ago. And he says that pinning down just one source can be incredibly difficult.

JOHN COWDEN: When you speak to a large number of the cases, you may find that actually they don't have anything in common. Some may have eaten bean spouts, some may have eaten tomatoes, some may have eaten lettuce, some may have contracted the disease from other people in the family or indeed from people that they don't even know are ill.

So that's why experts are working round the clock here in Germany to try to track down the source of this outbreak.